Long Chain Branched Polymers and Methods of Making Same

ABSTRACT

A polymer having a long chain branching content peaking at greater than about 20 long chain branches per million carbon atoms, and a polydispersity index of greater than about 10 wherein the long chain branching decreases to approximately zero at the higher molecular weight portion of the molecular weight distribution. A polymer having a long chain branching content peaking at greater than about 8 long chain branches per million carbon atoms, a polydispersity index of greater than about 20 wherein the long chain branching decreases to approximately zero at the higher molecular weight portion of the molecular weight distribution. A polymer having a long chain branching content peaking at greater than about 1 long chain branches per chain, and a polydispersity index of greater than about 10 wherein the long chain branching decreases to approximately zero at the higher molecular weight portion of the molecular weight distribution.

TECHNICAL FIELD

The present disclosure relates to novel polymer compositions and methodsof making and using same. More specifically, the present disclosurerelates to polymer compositions having long chain branching.

BACKGROUND

Polymeric compositions, such as polyethylene compositions, are used forthe production of a wide variety of articles. The use of a particularpolymeric composition in a particular application will depend on thetype of physical and/or mechanical properties displayed by the polymer.Thus, there is an ongoing need to develop polymers that display novelphysical and/or mechanical properties and methods for producing thesepolymers.

SUMMARY

Disclosed herein is a polymer having a long chain branching contentpeaking at greater than about 20 long chain branches per million carbonatoms, and a polydispersity index (M_(w)/M_(n)) of greater than about 10wherein the long chain branching decreases to approximately zero at thehigher molecular weight portion of the molecular weight distribution.

Further disclosed herein is a polymer having a long chain branchingcontent peaking at greater than about 8 long chain branches per millioncarbon atoms, a polydispersity index of greater than about 20 whereinthe long chain branching decreases to approximately zero at the highermolecular weight portion of the molecular weight distribution.

Also disclosed herein is a polymer having a long chain branching contentpeaking at greater than about 1 long chain branches per chain, and apolydispersity index of greater than about 10 wherein the long chainbranching decreases to approximately zero at the higher molecular weightportion of the molecular weight distribution.

Also disclosed herein is a method of polymerizing a monomer comprisingcontacting the monomer with a chromium-supported catalyst underconditions suitable for the formation of a polymer; and recovering thepolymer wherein the chromium supported catalyst comprises a silicasupport having a surface area of less than about 200 m²/g and whereinthe polymer has a long chain branching content peaking at greater thanabout 20 long chain branches per million carbon atoms.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-7 are plots of the long chain branching content as a function ofmolecular weight for the samples from the examples.

DETAILED DESCRIPTION

Disclosed herein are novel polymer compositions and methods of makingsame. In an embodiment the polymer compositions comprise long chainbranched polymers designated (LCBP). Hereinafter, the polymer refersboth to the material collected as the product of a polymerizationreaction and the polymeric composition comprising the polymer and one ormore additives.

LCBPs may be produced using catalysts comprising chromium and alow-surface area support. Hereinafter, such catalysts are termedcatalysts for production of long chain branched polymers and designatedCr—X. In an embodiment, a LCBP is prepared by a methodology that employsa Cr—X catalyst and at least one modification. Herein, a modificationrefers to a specified reactant and/or reaction conditions that isemployed in preparation of the polymer, as described in more detailherein.

In an embodiment, the LCBP is prepared by a methodology employing a Cr—Xcatalyst and at least one Class A modification. Herein, a Class Amodification refers to a change in the type of catalyst employed in thereaction for preparation of a LCBP. In an embodiment, the Class Amodification comprises activating the Cr—X catalyst at a temperature ofless than about 650° C. In an embodiment, the Class A modificationcomprises adjusting the amount of Cr present on the support to provide achromium distribution of greater than about 2 chromium atoms per nm² ofsupport. In an embodiment the Class A modification comprisesincorporating titanium into the Cr—X.

In an embodiment, the LCBP is prepared by a methodology employing a Cr—Xcatalyst and a Class B modification. Herein, a Class B modificationrefers to a change in the type and/or amount of reactants employed inthe reaction for preparation of a LCBP. In an embodiment the Class Bmodification comprises providing a monomer concentration in the reactorthat is less than about 1 mole/liter (mol/L). In an embodiment, theClass B modification comprises employing a cocatalyst in the reactionfor production of the LCBP. LCBPs and methodologies for preparation of aLCBP are described in more detail herein.

In an embodiment, a Cr—X catalyst is used to prepare a LCBP of the typedisclosed herein. The Cr—X catalyst may comprise chromium and a catalystsupport.

In an embodiment, the support of the Cr—X catalyst may primarily includean inorganic oxide such as silica, alumina, aluminophosphates, ormixtures thereof. In an embodiment, the support contains greater thanabout 50 percent (%) silica, alternatively greater than about 80%silica, by weight of the support. The support may further includeadditional components that do not adversely affect the catalyst system,such as zirconia, alumina, boria, thoria, magnesia, or mixtures thereof.

In an embodiment, the support comprises a precipitated silica. Forexample, the support may comprise a precipitated or gelled silica.Herein, a gelled or precipitated silica contains a three-dimensionalnetwork of primary silica particles.

In an embodiment, the support is a reinforced support. Such reinforcedsupports may be prepared by any suitable methodology. For example, areinforced support suitable for use in the present disclosure isprepared by aging of the support material. For example, the support maybe alkaline aged by contacting the support with an alkaline solutioncontaining one or more basic compounds (e.g., bases, buffer) having a pHof from about 8 to about 13, alternatively from about 9 to about 12, oralternatively from about 9 to about 10 at a temperature of from about60° C. to about 90° C., or from about 70° C. to about 85° C., or atabout 80° C. The alkaline solution may be comprised of any componentswhich provide a solution pH in the disclosed ranges and are compatiblewith the other components of the composition. For example, the alkalinesolution may comprise ammonium hydroxide, potassium hydroxide, sodiumhydroxide, trialkylammonium hydroxide, sodium silicate and the like.Other suitable compounds and amounts effective to provide a solution inthe disclosed pH ranges may be utilized.

In an alternative embodiment, the support may be aged by contact with aneutral solution (neutral aging) having a pH of about 7 at a temperatureof from about 60° C. to about 90° C., or from about 70° C. to about 85°C., or at about 80° C.

Optional aging of the support (alkaline or neutral) may be carried outfor a time period sufficient to lower the surface area of the support toless than about 80% of the original value of the surface area of anotherwise similar material that has not been aged, alternatively to lessthan about 70%, 60%, or 50%. In an embodiment, the aging is carried outfor a period of time of from about 1 hour to about 24 hours, or fromabout 2 hours to about 10 hours, or from about 3 hours to about 6 hours.

In an embodiment, a method for preparation of a reinforced supportfurther comprises drying the support. The support may be dried to removesolvent and form a dried support. The drying may be carried out in atemperature range of from about 25° C. to about 300° C., alternativelyfrom about 50° C. to about 200° C., or alternatively from about 80° C.to about 150° C. and for a time period of from about 0.1 min to about 10hours, alternatively from about 0.2 min to about 5 hours, oralternatively from about 30 min to about 1 hour. In an embodiment, amethod for preparation of a reinforced support further comprisescalcining the dried support to form a dried calcined support. Forexample, the dried support may be calcined in the presence of air at atemperature in the range of from about 400° C. to about 1,000° C.,alternatively from about 500° C. to about 900° C., and for a time periodof from about 1 hour to about 30 hours, alternatively from about 2 hoursto about 20 hours, or alternatively from about 5 hours to about 12hours.

In an embodiment, the reinforced support is prepared by hydrothermaltreatment (steaming) of the support to lower the surface area.Alternatively, the reinforced support is prepared by thermal sinteringof the support. Alternatively, the reinforced support is prepared bychemical sintering of the support such as by using a fluxing agent likesodium ions or potassium ions during thermal treatment. Alternatively,the reinforced support is prepared by a methodology involving asecondary deposition of silica onto a silica, using for example sodiumsilicate, or tetraethylorthosilicate, or SiCl₄, etc. Alternatively thereinforced support is prepared by a combination of two or more of thedisclosed methodologies. For example the reinforced support may beprepared by alkaline aging and hydrothermal treatment.

In an embodiment, the support is a low surface area support. Herein, alow surface area support has a surface area of less than about 250 m²/g,alternatively less than about 200 m²/g, alternatively less than about150 m²/g, or alternatively less than about 125 m²/g. Further, the porevolume of the support may range from about 0.5 cubic centimeters pergram (cc/g) to about 3.5 cc/g or alternatively from about 0.8 cc/g toabout 3 cc/g. Hereinafter for simplicity, the disclosure will refer tosilica as the support although other supports such as have beendescribed herein may be contemplated.

The amount of support present in the catalyst (e.g., Cr—X) may rangefrom about 90% to about 99.9% by weight of the catalyst, alternativelyfrom about 95% to about 99.9%, or from about 97% to about 99.9%. In anembodiment, the support comprises the remainder of the catalyst when allother components are accounted for.

In an embodiment, the catalyst comprises chromium. Chromium may beincluded in the Cr—X catalyst by contacting of a chromium-containingcompound with a support of the type previously described herein. Thechromium-containing compound may comprise a water-soluble chromiumcompound. Alternatively, the chromium-containing compound comprises ahydrocarbon-soluble chromium compound. Examples of water-solublechromium compounds include without limitation chromium oxide, chromiumtrioxide, chromium acetate, chromium nitrate, or combinations thereof.Examples of hydrocarbon-soluble chromium compounds include withoutlimitation tertiary butyl chromate, a diarene chromium (0) compound,biscyclopentadienyl chromium(II), chromium (III) acetylacetonate, orcombinations thereof. In one embodiment, the chromium-containingcompound may be a chromium (II) compound, chromium (III) compound, orcombinations thereof. Suitable chromium (III) compounds include, but arenot limited to chromium carboxylates, chromium naphthenates, chromiumhalides, chromium sulfate, chromium nitrate, chromium dionates, orcombinations thereof. Specific chromium (III) compounds include, but arenot limited to, chromium (III) sulfate, chromium (III) chloride,chromium (III) nitrate, chromic bromide, chromium (III) acetylacetonate,chromium (III) acetate. Suitable chromium (II) compounds include, butare not limited to chromous chloride, chromous bromide, chromous iodide,chromium (II) sulfate, chromium (II) acetate, or combinations thereof.

The amount of chromium present in the catalyst (e.g., Cr—X) may rangefrom about 0.01% to about 10% by weight of the catalyst, alternativelyfrom about 0.5% to about 5%, or from about 1.0% to about 3%. Herein, thepercentage chromium refers to the final percent chromium associated withthe support material by total weight of the material after allprocessing steps.

In an embodiment, chromium is present in an amount sufficient to providea chromium(VI) distribution of greater than about 2 chromium atoms pernm² of support, alternatively greater than about 2.5 chromium atoms pernm² of support, or alternatively greater than about 3 chromium atoms pernm² of support. In some embodiments, the chromium (VI) distribution isthe average distribution based on the use of more than one catalysttype. For example, a chromium distribution falling within the valuesdisclosed herein may be achieved through the use a conventionalCr-supported catalyst and a Cr—X catalyst of the type disclosed herein.

In another embodiment, a method of preparing a Cr—X catalyst comprisescontacting a support of the type disclosed herein with achromium-containing compound to form Cr-silica. The chromium-containingcompound may be a water-soluble compound or a hydrocarbon-solublecompound such as those previously described herein and may be introducedto the support using any suitable contacting technique. For example, thechromium-containing compound may be contacted with the silica supportusing techniques such as ion-exchange, incipient wetness, pore fill,impregnation, etc.

The Cr-silica may then be dried to remove solvent at temperaturesranging from about 25° C. to about 300° C., alternatively from about 50°C. to about 200° C., or alternatively from about 80° C. to about 150° C.and for a time period of from about 0.1 min to about 10 hours,alternatively from about 0.2 min to about 5 hours, alternatively fromabout 30 min to about 1 hour, thereby forming a dried Cr-silica.

In an embodiment, the dried Cr-silica is activated to produce an activecatalyst, alternatively an active polymerization catalyst. The driedCr-silica of the present disclosure may be activated using various typesof activator equipment. Any vessel or apparatus may be utilized toactivate the dried Cr-silica including for example rotary calciners,static pan driers, or fluidized beds. Such equipment may operate in astatic, batch, or continuous mode. For the static or batch mode, avessel or apparatus containing the catalyst bed may be subjectedsequentially to various stages of the activation process. For thecontinuous mode, the stages of the process can occur in a series ofzones through which the dried Cr-silica passes on its path through theactivation apparatus.

In an embodiment, the dried Cr-silica is activated in a fluidized bedactivator. In a fluidized bed activator, gas may flow upward through agrid plate containing many small holes upon which the dried Cr-silica ispositioned. The gas may contain various compounds to create a desirableprocess conditions. The dried Cr-silica may be mixed in the gas as itflows creating a fluid-like flow. This is often referred to asfluidization or fluidizing.

The activation may further comprise heating the dried Cr-silica to adesired temperature in one or more stages. As used herein, the term“stages” refers to heating the dried Cr-silica to a desired temperatureand holding the temperature for a period of time. A stage may beperformed when the dried Cr-silica is in a stationary position or bymoving the dried Cr-silica through various locations and may comprise aramp up time to a desired temperature and holding the dried Cr-silica atthat temperature for a certain hold time. For two or more stages, therewill be two or more ramp up times, two or more desired temperatures, andtwo or more hold times. The ramp up times may be the same or different,for example the ramp up time may be instantaneous (e.g., preheatedenvironment) to less than about 3 hours.

The temperature(s) at which the dried Cr-silica is activated may beadjusted to achieve a user-desired result. For example, if the driedCr-silica activation is used to fulfill a condition for preparation of aLCBP (e.g., a Class A modification), the activation may be carried outby heating the dried Cr-silica to temperatures of less than about 650°C., alternatively less than about 625° C., or alternatively less thanabout 600° C. In an alternative embodiment, the dried Cr-silicaactivation is not used to fulfill a condition for the preparation of aLCBP. In such an embodiment, the dried Cr-silica may be activated attemperature(s) in a range of from about 400° C. to about 1000° C.,alternatively from about 600° C. to about 900° C., alternatively fromabout 750° C. to about 900° C.

Activation also causes oxidation of any of the trivalent form ofchromium (Cr(III)) to the hexavalent form (Cr(VI)) and thenstabilization of the Cr(VI) form. As used herein, the term“stabilization” refers to the activation process resulting in the Cr(VI)form of the catalyst. The activation process may convert from about 10to about 100% of Cr(III) to Cr(VI), or from about 30 to about 80%, orfrom about 35 to about 65% and yield from about 0.1 to about 5% Cr(VI),from about 0.5 to about 3.0%, or from about 1.0 to about 3.0% whereinthe percentage refers to the weight percent chromium (VI) based on thetotal weight of the catalyst. In an embodiment, the dried Cr-silica isactivated as described herein to form a Cr—X.

In an embodiment, a LCBP is prepared using a titanium-containing Cr—Xcatalyst. The titanium-containing Cr—X catalyst may comprise chromiumand a support, both of the type previously disclosed herein.Additionally, the titanium-containing Cr—X catalyst comprises titanium.

The silica-titanium Cr—X catalyst may be prepared by cogelation or bycontacting a support of the type previously disclosed herein with asolution or vapor containing a titanium compound. For example, one canuse an aqueous solution comprising a trivalent titanium (Ti³)-containingcompound and/or a tetravalent titanium (Ti⁴)-containing compound. TheTi⁴⁺-containing compound may be any compound that comprises tetravalenttitanium, alternatively the Ti⁴⁺-containing compound may be any compoundthat is soluble in an aqueous solution and able to release a Ti⁴⁺species into solution. Examples of Ti⁴⁺-containing compounds suitablefor use in the present disclosure include without limitation titanylnitrate. The Ti³⁺-containing compound may be any compound that comprisestrivalent titanium, alternatively the Ti³⁺ containing compound may beany compound that is soluble in an aqueous solution and able to releasea Ti³⁺ species into solution. Examples of suitable Ti³⁺-containingcompounds include without limitation TiCl₃, (Ti)₂(SO₄)₃, Ti(OH)Cl₂,TiBr₃, and the like.

In an embodiment, the support is contacted with the Ti³⁺-containingcompound and/or Ti⁴⁺-containing compound by impregnation. Thetitanium-containing support may then be dried to remove solvent and forma dried titanium-containing support. The drying may be carried out in atemperature range of from about 25° C. to about 300° C., alternativelyfrom about 50° C. to about 200° C., or alternatively from about 80° C.to about 150° C. and for a time period of from about 0.1 min to about 10hours, alternatively from about 0.2 min to about 5 hours, oralternatively from about 30 min to about 1 hour. In some embodiments,the drying is carried out in an inert atmosphere (e.g. under vacuum, He,Ar or nitrogen gas).

In an alternative embodiment, titanium can be applied to the support byvapor phase deposition or by impregnation of a non-aqueous solution oftitanium. Suitable titanium compounds used in this embodiment includewithout limitation halides and alkoxides of titanium.

The method may further comprise calcining the dried titanium-containingsupport in the presence of air to oxidize the Ti³⁺ to Ti⁴⁺ and attachthe titanium to the support and form a dried calcinedtitanium-containing support. For example, the dried titanium-containingsupport may be calcined in the presence of air at a temperature in therange of from about 400° C. to about 1,000° C., alternatively from about500° C. to about 900° C., and for a time period of from about 1 hour toabout 30 hours, alternatively from about 2 hours to about 20 hours,alternatively from about 5 hours to about 12 hours.

The method may further comprise adding a chromium-containing compound tothe dried calcined titanium-containing support to form a Cr/Ti-silica.The chromium-containing compound may be a water-soluble compound or ahydrocarbon-soluble compound such as those previously described hereinand may be introduced to the dried calcined titanium-containing supportusing the contacting techniques also previously described herein. TheCr/Ti-silica may be dried again to remove solvent introduced by theaddition of the chromium-containing compound at temperatures rangingfrom 25° C. to about 300° C., alternatively from about 50° C. to about200° C., or alternatively from about 80° C. to about 150° C. In oneembodiment, the Cr/Ti-silica may then be activated via a secondcalcination step by heating it in an oxidizing environment to produce atitanium-containing Cr—X. Such activations may be carried out usingprocedures and equipment of the type previously disclosed herein (e.g.,fluidized bed). For example, the Cr/Ti-silica may be calcined in thepresence of air at a temperature in the range of from about 400° C. toabout 1,000° C., alternatively from about 500° C. to about 850° C. andfor a time period of from about 1 min to about 10 hours, alternativelyfrom about 20 min to about 5 hours, or alternatively from about 1 toabout 3 hours to produce the titanium-containing Cr—X.

In another embodiment, a method of preparing a titanium-containing Cr—Xcatalyst comprises contacting a support with a chromium-containingcompound to form a Cr-supported composition. The chromium-containingcompound may be a water-soluble compound or a hydrocarbon-solublecompound such as those previously described herein and may be introducedto the support using the contacting techniques also previously describedherein. The Cr-supported composition may be dried to remove solvent attemperatures ranging from about 25° C. to about 300° C., alternativelyfrom about 50° C. to about 200° C., or alternatively from about 80° C.to about 150° C. and for a time period of from about 0.1 min to about 10hours, alternatively from about 0.2 min to about 5 hours, alternativelyfrom about 30 min to about 1 hour, thereby forming a dried Cr-supportedcomposition. The method may further comprise contacting the driedCr-supported composition with a Ti³⁺-containing compound and/orTi⁴⁺-containing compound to form a Cr/Ti-silica. The Ti³⁺-containingcompound may be contacted with the dried Cr-supported composition usingany of the contacting techniques previously described herein. In anembodiment, the dried Cr-supported composition is contacted with aTi³⁺-containing compound by impregnation with a Ti³⁺-aqueous saltsolution to form a Cr/Ti-silica. The method further comprises activatingthe Cr/Ti-silica by drying and/or calcining the Cr/Ti-silica in thepresence of air to oxidize the Ti³⁺ to Ti⁴⁺ and attach the titanium tothe silica. Such activations may be carried out using procedures andequipment of the type previously disclosed herein (e.g., fluidized bed).For example, the Cr/Ti-silica may be heated in the presence of air at atemperature in the range of from about 400° C. to about 1,000° C.,alternatively from about 500° C. to about 850° C. and for a time periodof from about 1 min to about 10 hours, alternatively from about 20 minto about 5 hours, alternatively from about 1 hour to about 3 hours toproduce the titanium-containing Cr—X catalyst.

In another embodiment, a method of preparing a catalyst comprisescontacting a support of the type disclosed herein with a Ti³⁺-containingcompound and/or Ti⁴⁺-containing compound and a chromium-containingcompound to form a metallated support. The contacting of the supportwith the Ti³⁺-containing compound and/or Ti⁴⁺-containing compound andchromium-containing compound may be simultaneous; alternatively thecontacting may be carried out sequentially (e.g., Ti³⁺ and/or Ti⁴⁺followed by Cr or vice-versa). The Ti³⁺-containing compound and/orTi⁴⁺-containing compound and chromium-containing compound may be of thetypes previously described herein and may be introduced to the support(e.g., low surface area silica) using the contacting techniques alsopreviously described herein to form a metallated silica. The metallatedsilica may be dried to remove solvent at temperatures ranging from about25° C. to about 300° C., alternatively from about 50° C. to about 200°C., or alternatively from about 80° C. to about 150° C. and for a timeperiod of from about 0.1 min to about 10 hours, alternatively from about0.2 min to about 5 hours, alternatively from about 30 min to about 1hour, thereby forming a dried metallated silica. In one embodiment, thedried metallated silica may then be activated via a calcination step byheating it in an oxidizing environment. Such activations may be carriedout using procedures and equipment of the type previously disclosedherein (e.g., fluidized bed). For example, the dried metallated silicamay be heated in the presence of air at a temperature in the range offrom about 400° C. to about 1,000° C., alternatively from about 500° C.to about 850° C. and for a time of from about 1 min to about 10 hours,alternatively from about 20 min to about 5 hours, alternatively fromabout 1 to about 3 hours to produce the titanium-containing Cr—X.

In the embodiments wherein a titanium-containing Cr—X catalyst isformed, the amount of titanium utilized may be sufficient to provide apercentage titanium of from about 0.1% to about 10% by weight of thecatalyst, or alternatively from about 0.5% to about 8%, alternativelyfrom about 1% to about 5%. Herein, the percentage titanium refers to thefinal percent titanium associated with the support material by totalweight of the material after all processing steps.

Alternatively, in embodiments wherein a titanium-containing Cr—Xcatalyst is formed, the amount of titanium utilized may be sufficient toprovide a titanium distribution of greater than about 2 titanium atomsper nm² of support, alternatively greater than about 2.5 titanium atomsper nm² of support, or alternatively greater than about 3 titanium atomsper nm² of support.

It is contemplated that the temperature(s) at which the compositioncomprising chromium, titanium and silica (e.g., Cr/Ti-silica, metallatedsilica) is activated to form an activated catalyst may be adjusted toachieve a user desired result. For example, if activation of thecomposition comprising chromium, titanium and silica is used to fulfilla condition for preparation of a LCBP (e.g., a Class A modification) theactivation may be carried out by heating the catalyst comprisingchromium, titanium and silica to temperatures of less than about 650°C., alternatively less than about 625° C., or alternatively less thanabout 600° C. In an alternative embodiment, if activation of thecomposition comprising chromium, titanium and silica is used to fulfilla condition for preparation of a LCBP (e.g., a Class A modification) theactivation may be carried out by heating the catalyst comprisingchromium, titanium and silica to temperatures of greater than about 700°C., alternatively greater than about 800° C., or alternatively greaterthan about 850° C.

In an embodiment, a catalyst for use in the preparation of a LCBP has acatalytic activity of greater than about 750 grams polymer product pergram catalyst used (g/g), alternatively greater than about 1000 g/g,alternatively greater than about 1500 g/g, or alternatively greater thanabout 2000 g/g.

In an embodiment, a LCBP of the type disclosed herein is prepared by amethodology employing a Cr—X catalyst and a Class A modification. In anembodiment, the Class A modification comprises activating the Cr—Xcatalyst at a temperature of less than about 650° C. as describedpreviously herein. In an embodiment, the Class A modification comprisesadjusting the amount of Cr on the support (e.g., low surface areasilica) to provide a chromium distribution of greater than about 2chromium atoms per nm² of support as described previously herein. In anembodiment, the Class A modification comprises incorporating titaniuminto the Cr—X catalyst to form a titanium-containing Cr—X catalyst asdisclosed previously herein.

The Class A modifications disclosed herein result in catalysts that maybe suitably employed in an olefin polymerization method. The catalystsof the present disclosure are suitable for use in any olefinpolymerization method, using various types of polymerization reactors.In an embodiment, a polymer of the present disclosure is produced by anyolefin polymerization method, using various types of polymerizationreactors. As used herein, “polymerization reactor” includes any reactorcapable of polymerizing olefin monomers to produce homopolymers and/orcopolymers. Homopolymers and/or copolymers produced in the reactor maybe referred to as resin and/or polymers. The various types of reactorsinclude, but are not limited to those that may be referred to as batch,slurry, gas-phase, solution, high pressure, tubular, autoclave, or otherreactor and/or reactors. Gas phase reactors may comprise fluidized bedreactors or staged horizontal reactors. Slurry reactors may comprisevertical and/or horizontal loops. High pressure reactors may compriseautoclave and/or tubular reactors. Reactor types may include batchand/or continuous processes. Continuous processes may use intermittentand/or continuous product discharge or transfer. Processes may alsoinclude partial or full direct recycle of un-reacted monomer, un-reactedcomonomer, catalyst and/or co-catalysts, diluents, and/or othermaterials of the polymerization process.

Polymerization reactor systems of the present disclosure may compriseone type of reactor in a system or multiple reactors of the same ordifferent type, operated in any suitable configuration. Production ofpolymers in multiple reactors may include several stages in at least twoseparate polymerization reactors interconnected by a transfer systemmaking it possible to transfer the polymers resulting from the firstpolymerization reactor into the second reactor. Alternatively,polymerization in multiple reactors may include the transfer, eithermanual or automatic, of polymer from one reactor to subsequent reactoror reactors for additional polymerization. Alternatively, multi-stage ormulti-step polymerization may take place in a single reactor, whereinthe conditions are changed such that a different polymerization reactiontakes place.

The desired polymerization conditions in one of the reactors may be thesame as or different from the operating conditions of any other reactorsinvolved in the overall process of producing the polymer of the presentdisclosure. Multiple reactor systems may include any combinationincluding, but not limited to multiple loop reactors, multiple gas phasereactors, a combination of loop and gas phase reactors, multiple highpressure reactors or a combination of high pressure with loop and/or gasreactors. The multiple reactors may be operated in series or inparallel. In an embodiment, any arrangement and/or any combination ofreactors may be employed to produce the polymer of the presentdisclosure.

According to one embodiment, the polymerization reactor system maycomprise at least one loop slurry reactor. Such reactors arecommonplace, and may comprise vertical or horizontal loops. Monomer,diluent, catalyst system, and optionally any comonomer may becontinuously fed to a loop slurry reactor, where polymerization occurs.Generally, continuous processes may comprise the continuous introductionof a monomer, a catalyst, and/or a diluent into a polymerization reactorand the continuous removal from this reactor of a suspension comprisingpolymer particles and the diluent. Reactor effluent may be flashed toremove the liquids that comprise the diluent from the solid polymer,monomer and/or comonomer. Various technologies may be used for thisseparation step including but not limited to, flashing that may includeany combination of heat addition and pressure reduction; separation bycyclonic action in either a cyclone or hydrocyclone; separation bycentrifugation; or other appropriate method of separation.

Typical slurry polymerization processes (also known as particle-formprocesses) are disclosed in U.S. Pat. Nos. 3,248,179, 4,501,885,5,565,175, 5,575,979, 6,239,235, 6,262,191 and 6,833,415, for example;each of which are herein incorporated by reference in their entirety.

Suitable diluents used in slurry polymerization include, but are notlimited to, the monomer being polymerized and hydrocarbons that areliquids under reaction conditions. Examples of suitable diluentsinclude, but are not limited to, hydrocarbons such as propane,cyclohexane, isobutane, n-butane, n-pentane, isopentane, neopentane, andn-hexane. Some loop polymerization reactions can occur under bulkconditions where no diluent is used. An example is polymerization ofpropylene monomer as disclosed in U.S. Pat. No. 5,455,314, which isincorporated by reference herein in its entirety.

According to yet another embodiment, the polymerization reactor maycomprise at least one gas phase reactor. Such systems may employ acontinuous recycle stream containing one or more monomers continuouslycycled through a fluidized bed in the presence of the catalyst underpolymerization conditions. A recycle stream may be withdrawn from thefluidized bed and recycled back into the reactor. Simultaneously,polymer product may be withdrawn from the reactor and new or freshmonomer may be added to replace the polymerized monomer. Such gas phasereactors may comprise a process for multi-step gas-phase polymerizationof olefins, in which olefins are polymerized in the gaseous phase in atleast two independent gas-phase polymerization zones while feeding acatalyst-containing polymer formed in a first polymerization zone to asecond polymerization zone. One type of gas phase reactor is disclosedin U.S. Pat. Nos. 4,588,790, 5,352,749, and 5,436,304, each of which isincorporated by reference in its entirety herein.

According to still another embodiment, a high pressure polymerizationreactor may comprise a tubular reactor or an autoclave reactor. Tubularreactors may have several zones where fresh monomer, initiators, orcatalysts are added. Monomer may be entrained in an inert gaseous streamand introduced at one zone of the reactor. Initiators, catalysts, and/orcatalyst components may be entrained in a gaseous stream and introducedat another zone of the reactor. The gas streams may be intermixed forpolymerization. Heat and pressure may be employed appropriately toobtain optimal polymerization reaction conditions.

According to yet another embodiment, the polymerization reactor maycomprise a solution polymerization reactor wherein the monomer iscontacted with the catalyst composition by suitable stirring or othermeans. A carrier comprising an organic diluent or excess monomer may beemployed. If desired, the monomer may be brought in the vapor phase intocontact with the catalytic reaction product, in the presence or absenceof liquid material. The polymerization zone is maintained attemperatures and pressures that will result in the formation of asolution of the polymer in a reaction medium. Agitation may be employedto obtain better temperature control and to maintain uniformpolymerization mixtures throughout the polymerization zone. Adequatemeans are utilized for dissipating the exothermic heat ofpolymerization.

Polymerization reactors suitable for the present disclosure may furthercomprise any combination of at least one raw material feed system, atleast one feed system for catalyst or catalyst components, and/or atleast one polymer recovery system. Suitable reactor systems for thepresent invention may further comprise systems for feedstockpurification, catalyst storage and preparation, extrusion, reactorcooling, polymer recovery, fractionation, recycle, storage, loadout,laboratory analysis, and process control.

Conditions that are controlled for polymerization efficiency and toprovide polymer properties include, but are not limited to temperature,pressure, type and quantity of catalyst or co-catalyst, and theconcentrations of various reactants. Polymerization temperature canaffect catalyst productivity, polymer molecular weight and molecularweight distribution. Suitable polymerization temperatures may be anytemperature below the de-polymerization temperature, according to theGibbs Free Energy Equation. Typically, this includes from about 60° C.to about 280° C., for example, and/or from about 70° C. to about 110°C., depending upon the type of polymerization reactor and/orpolymerization process.

Suitable pressures will also vary according to the reactor andpolymerization process. The pressure for liquid phase polymerization ina loop reactor is typically less than 1000 psig. Pressure for gas phasepolymerization is usually at about 200-500 psig. High pressurepolymerization in tubular or autoclave reactors is generally run atabout 20,000 to 75,000 psig. Polymerization reactors can also beoperated in a supercritical region occurring at generally highertemperatures and pressures. Operation above the critical point of apressure/temperature diagram (supercritical phase) may offer advantages.

In an embodiment, the LCBP is prepared by a methodology employing a Cr—Xcatalyst and a Class B modification. In an embodiment the Class Bmodification comprises providing that the concentration of monomerpresent in the reactor is less than about 1 mole/liter (mol/L),alternatively less than about 0.75 mol/L, or alternatively less thanabout 0.5 mol/L. Examples of monomers suitable for use in the presentdisclosure include without limitation mono-olefins containing 2 to 8carbon atoms per molecule such as ethylene, propylene, 1-butene,1-pentene, 1-hexene, and 1-octene. In an embodiment, the monomercomprises ethylene. In embodiments wherein the monomer is a gas (e.g.ethylene), the polymerization or oligomerization reaction can be carriedout under a monomer gas pressure. When the polymerization oroligomerization reaction produces polyethylene or alpha olefins, thereaction pressure can be the monomer ethylene pressure. In someembodiments, the ethylene pressure can be greater than 0 psig (0 KPa);alternatively, greater than 50 psig (344 KPa); alternatively, greaterthan 100 psig (689 KPa); or alternatively, greater than 150 psig (1.0MPa). In other embodiments, the ethylene pressure can range from 0 psig(0 KPa) to 5,000 psig (34.5 MPa); alternatively, 50 psig (344 KPa) to4,000 psig (27.6 MPa); alternatively, 100 psig (689 KPa) to 3,000 psig(20.9 MPa); or alternatively, 150 psig (1.0 MPa) to 2,000 psig (13.8MPa). In some cases when ethylene is the monomer, inert gases can form aportion of the total reaction pressure. In the cases where inert gasesform a portion of the reaction pressure, the previously stated ethylenepressures can be the applicable ethylene partial pressures of thepolymerization or oligomerization reaction. In the situation where themonomer provides all or a portion of the polymerization oroligomerization reaction pressure, the reaction system pressure candecrease as the gaseous monomer is consumed. In this situation,additional gaseous monomer and/or inert gas can be added to maintain adesired polymerization or oligomerization reaction pressure. Inembodiments, additional gaseous monomer can be added to thepolymerization or oligomerization reaction at a set rate (e.g. for acontinuous flow reactor), at different rates (e.g. to maintain a setsystem pressure in a batch reactor). In other embodiments, thepolymerization or oligomerization reaction pressure can be allowed todecrease without adding any additional gaseous monomer and/or inert gas.

In an embodiment, the Class B modification comprises employing acocatalyst in the reaction for production of the LCBP. Generally, thecocatalyst can be any organometallic compound capable of activating thecatalyst (e.g., Cr—X) to polymerize or oligomerize olefins. Suitablecocatalysts can include without limitation monomeric or oligomeric metalalkyls, metal aryls, metal alkyl-aryls comprising at least one of themetals selected from the group consisting of B, Al, Be, Mg, Ca, Sr, Ba,Li, Na, K, Rb, Cs, Zn, Cd, and Sn. In embodiments, the cocatalyst can beselected from the group consisting of organoaluminum compounds,organoboron compounds, organolithium compounds, or mixtures thereof. Insome embodiments, the cocatalyst can be an organoaluminum compound.Applicable organoaluminum compounds can include without limitationtrialkylaluminums, alkylaluminum halides, alumoxanes or mixture thereof.In some embodiments, the organoaluminum compound can betrimethylaluminum, triethylaluminum, diethylaluminum chloride,diethylaluminum ethoxide, diethylaluminum cyanide, diisobutylaluminumchloride, triisobutylaluminum, ethylaluminum sesquichloride,methylalumoxane (MAO), modified methylalumoxane (MMAO), isobutylalumoxanes, t-butyl alumoxanes, or mixtures thereof. In otherembodiments, the organoaluminum compounds can include without limitationmethylalumoxane (MAO), modified methylalumoxane (MMAO), isobutylalumoxanes, t-butyl alumoxanes, or mixtures thereof. In otherembodiments, the cocatalyst can be methylalumoxane, modifiedmethylalumoxane, or mixtures thereof. In yet other embodiments, thecocatalyst can be methylalumoxane; alternatively, modifiedmethylalumoxane; isobutylalumoxane (IBAO); or alternatively, partiallyhydrolyzed trialkylaluminum.

In an embodiment, the cocatalyst comprises a compound represented by thegeneral formula AlR₃ or BR₃. Alternatively, the cocatalyst istriethylboron (TEB). The cocatalyst can be present in the reactor in anamount of greater than about 1 ppm, alternatively greater than about 5ppm, or alternatively greater than about 8 ppm based on the weight ofthe solvent or diluent in systems employing such solvent or diluent.When no solvent or diluent is used, the catalyst (e.g., Cr—X) may beimpregnated with the cocatalyst in an amount that provides for acocatalyst to chromium mole ratio in the range of from about 0.1:1 toabout 100:1, alternatively from about 0.5:1 to about 50:1, or from about1:1 to 10:1.

In an embodiment, a method of making a LCBP of the type disclosed hereincomprises employing a Cr—X catalyst and at least one Class Amodification, alternatively a Cr—X catalyst and at least one Class Bmodification, or alternatively a Cr—X catalyst, at least one Class Amodification and at least one Class B modification. For example, amethod of making a LCBP of the type disclosed herein may compriseemploying a Cr—X catalyst wherein the Cr—X catalyst has been activatedat a temperature of less than about 650° C.

Alternatively, a method of making a LCBP of the type disclosed hereinmay comprise employing a Cr—X catalyst wherein the Cr—X catalyst hasbeen activated at a temperature of less than about 650° C. and theamount of Cr present in the reactor has been adjusted to provide achromium distribution of greater than about 2 chromium atoms per nm² ofsupport.

Alternatively, a method of making a LCBP of the type disclosed hereinmay comprise employing a Cr—X catalyst wherein the Cr—X catalyst hasbeen activated at a temperature of less than about 650° C., the amountof Cr present in the reactor has been adjusted to provide a chromiumdistribution of greater than about 2 chromium atoms per nm² of supportand titanium has been incorporated into the Cr—X catalyst.

Alternatively, a method of making a LCBP of the type disclosed hereinmay comprise employing a Cr—X catalyst wherein the Cr—X catalyst hasbeen activated at a temperature of less than about 650° C., the amountof Cr present in the reactor has been adjusted to provide a chromiumdistribution of greater than about 2 chromium atoms per nm² of support,titanium has been incorporated into the Cr—X catalyst, and theconcentration of monomer present in the reactor is less than about 1mole/liter (mol/L).

Alternatively, a method of making a LCBP of the type disclosed hereinmay comprise employing a Cr—X catalyst wherein the Cr—X catalyst hasbeen activated at a temperature of less than about 650° C., the amountof Cr present in the reactor has been adjusted to provide a chromiumdistribution of greater than about 2 chromium atoms per nm² of support,titanium has been incorporated into the Cr—X catalyst, the concentrationof monomer present in the reactor is less than about 1 mol/L, and acocatalyst is present in the reaction.

Alternatively, a method of making a LCBP of the type disclosed hereinmay comprise employing a Cr—X catalyst wherein the Cr—X catalyst hasbeen activated at a temperature of less than about 650° C. and acocatalyst comprising TEB present in the amounts previously disclosedherein. In an embodiment, the methodologies disclosed herein are used toproduce a LCBP of the type disclosed herein.

In an embodiment, a LCBP of the type described herein is characterizedby a density of from about 0.90 g/cc to about 0.97 g/cc, alternativelyfrom about 0.93 g/cc to about 0.97 g/cc, alternatively from about 0.92g/cc to about 0.965 g/cc, or alternatively from about 0.93 g/cc to about0.96 g/cc as determined in accordance with ASTM D1505.

In an embodiment, a LCBP produced using a catalyst of the type describedherein has a melt index, MI, in the range of from about 0 dg/min toabout 100 dg/min, alternatively from about 0.1 dg/min to about 10dg/min, alternatively from about 0.1 dg/min to about 3.0 dg/min, oralternatively from about 0.2 dg/min to about 2.0 dg/min. The melt index(MI) refers to the amount of a polymer which can be forced through anextrusion rheometer orifice of 0.0825 inch diameter when subjected to aforce of 2160 grams in ten minutes at 190° C., as determined inaccordance with ASTM D1238.

The molecular weight distribution (MWD) of the LCBP may be characterizedby the ratio of the weight average molecular weight (M_(w)) to thenumber average molecular weight (M_(n)), which is also referred to asthe polydispersity index (PDI) or more simply as polydispersity. Thenumber average molecular weight, M_(n), is the common average of themolecular weights of the individual polymers calculated by measuring themolecular weight of n polymer molecules, summing the weights, anddividing by n. The weight average molecular weight, M_(w), describes themolecular weight distribution of a polymer composition and is calculatedaccording to Equation 1:

$\begin{matrix}{{\overset{\_}{M}}_{w} = \frac{\sum\limits_{i}{N_{i}M_{i}^{2}}}{\sum\limits_{i}{N_{i}M_{i}}}} & (1)\end{matrix}$

where N_(i) is the number of molecules of molecular weight M_(i). A LCBPof the type disclosed herein may be characterized by a broad molecularweight distribution such that the PDI is equal to or greater than about10, alternatively greater than about 15, alternatively greater thanabout 20 or alternatively greater than about 25.

A LCBP of the type disclosed herein may be characterized by the degreeof long chain branching (LCB) present in the polymer. LCB was measuredusing the size-exclusion chromatography-multiangle light scatteringtechnique (SEC-MALS). Methods for the determination of long-chainbranching and long-chain branching distribution are described in anarticle by Yu et al. entitled “SEC-MALS method for the determination oflong-chain branching and long-chain branching distribution inpolyethylene,” Polymer (2005) Volume: 46, Issue: 14, Pages: 5165-5182which is incorporated by reference herein in its entirety.

In an embodiment, a LCBP of the type disclosed herein has a LCB contentpeaking that is determined as the number of LCB per million carbon atomswhich is designated X. In an embodiment, X is greater than about 8 LCBper million carbon atoms (LCB/10⁶ carbons), alternatively greater thanabout 15 LCB/10⁶ carbons, alternatively greater than about 20 LCB/10⁶carbons, or alternatively greater than about 30 LCB/10⁶ carbons. Herein,LCB content peaking refers to the maximum concentration of LCB as afunction of molecular weight. The number of LCB per 10⁶ total carbons iscalculated using the formula 1,000,000*M₀*B/M, where B is the number ofLCB per chain, M₀ is the molecular weight of the repeating unit, i.e.the methylene group, —CH₂—, for PE; and M is the molecular weight of aSEC slice where it is assumed that all macromolecules in the same SECslice have the same molecular weight. B is calculated according to thefollowing equation:

$g = {\frac{6}{B}\left\{ {{\frac{1}{2}\left( \frac{2 + B}{B} \right)^{1/2}{\ln \left\lbrack \frac{\left( {2 + B} \right)^{1/2} + (B)^{1/2}}{\left( {2 + B} \right)^{1/2} - (B)^{1/2}} \right\rbrack}} - 1} \right\}}$

wherein g is defined as the ratio of the mean square radius of gyrationof a branched polymer to that of a linear polymer of the same molecularweight. Both of the radius of gyration and the molecular weight weredetermined via SEC-MALS.

In an embodiment, a LCBP of the type disclosed herein has a LCB contentpeaking that is determined as the number of LCB per chain. In anembodiment, for a LCBP of the type disclosed herein B is greater thanabout 1.0 LCB/chain, alternatively greater than about 1.3, alternativelygreater than about 1.5, or alternatively greater than about 2.0.

In an embodiment, a LCBP of the type disclosed herein displays a LCBcontent that is characterized by a decrease in the amount of LCB toapproximately zero at the higher molecular weight portion of themolecular weight distribution. Herein, the higher molecular weightportion of the molecular weight distribution refers to a molecularweight of greater than about 10 million kg/mol.

In an embodiment, a methodology of the type disclosed herein is used toproduce a LCBP characterized by a long chain branching content peakingat greater than about 20 long chain branches per million carbon atoms,and a molecular weight distribution/PDI of greater than about 10 whereinthe long chain branching decreases to approximately zero at the highermolecular weight portion of the molecular weight distribution.

In an embodiment, a methodology of the type disclosed herein is used toproduce a LCBP characterized by a long chain branching content peakingat greater than about 20 long chain branches per million carbon atoms,and a molecular weight distribution of greater than about 15 wherein thelong chain branching decreases to approximately zero at the highermolecular weight portion of the molecular weight distribution.

In an embodiment, a methodology of the type disclosed herein is used toproduce a LCBP characterized by a long chain branching content peakingat greater than about 20 long chain branches per million carbon atoms,long chain branching content peaking at greater than about 1.0 longchain branches per chain and a molecular weight distribution of greaterthan about 10 wherein the long chain branching decreases toapproximately zero at the higher molecular weight portion of themolecular weight distribution.

In an embodiment, a methodology of the type disclosed herein is used toproduce a LCBP characterized by long chain branching content peaking atgreater than about 25 long chain branches per million carbon atoms, anda molecular weight distribution of greater than about 15 wherein thelong chain branching decreases to approximately zero at the highermolecular weight portion of the molecular weight distribution.

In an embodiment, a methodology of the type disclosed herein is used toproduce a LCBP characterized by a long chain branching content peakingat greater than about 30 long chain branches per million carbon atoms,and a molecular weight distribution of greater than about 15 wherein thelong chain branching decreases to approximately zero at the highermolecular weight portion of the molecular weight distribution.

In an embodiment, a methodology of the type disclosed herein is used toproduce a LCBP characterized by a long chain branching content peakingat greater than about 8 long chain branches per million carbon atoms, amolecular weight distribution of greater than about 20 wherein the longchain branching decreases to approximately zero at the higher molecularweight portion of the molecular weight distribution.

In an embodiment, a methodology of the type disclosed herein is used toproduce a LCBP characterized by a long chain branching content peakingat greater than about 1 long chain branches per chain, and a molecularweight distribution of greater than about 10 wherein the long chainbranching decreases to approximately zero at the higher molecular weightportion of the molecular weight distribution.

Polymer resins produced as disclosed herein (i.e., LCBPs) may be formedinto articles of manufacture or end use articles using techniques knownin the art such as extrusion, blow molding, injection molding, fiberspinning, thermoforming, and casting. For example, a polymer resin maybe extruded into a sheet, which is then thermoformed into an end usearticle such as a container, a cup, a tray, a pallet, a toy, or acomponent of another product. Examples of other end use articles intowhich the polymer resins may be formed include pipes, films, bottles,fibers, and so forth.

EXAMPLES

The following examples are given as particular embodiments of thedisclosure and to demonstrate the practice and advantages thereof. It isunderstood that the examples are given by way of illustration and arenot intended to limit the specification or the claims to follow in anymanner.

Cr—X catalysts of the type disclosed herein were prepared and used inthe formation of a LCBP of the type disclosed herein. Chromium in theform of chromium acetate was impregnated onto a low surface area silicafrom methanol to a loading of approximately 1.2 Cr/nm². The low surfacearea silicas used were SYLOX SD or SM500 which are commerciallyavailable from W.R. Grace. SYLOX SD has a surface area of approximately100 m²/g and a pore volume of 1.2 mL/g. SYLOX SD is reported to be a“hybrid” between silica gel and precipitated silica. In anotherexperiment a precipitated silica, SM500 was used. SM500 had a surfacearea of 102 m²/g and a pore volume of 1.1 mL/g. The silica impregnatedwith chromium was then dried in a vacuum oven at 100° C. for 12 hours.Cr/silica-titania catalysts were made by first drying the Cr-impregnatedSYLOX SD silica at 200° C. overnight, then impregnating titaniumtetraisopropoxide from dry heptane to a level of 3 wt % Ti, thenevaporating the solvent away. Finally, each dried catalyst was sizedthrough a 35 mesh screen.

To activate the catalyst, about 10 grams was placed in a 4.5 cm quartztube fitted with a sintered quartz disk at the bottom. While thecatalyst was supported on the disk, dry air was blown up through thedisk at a linear velocity of 3.0 cm/s. An electric furnace around thequartz tube was then turned on and the temperature was raised at therate of 400° C./h to the desired temperature, usually 800° C. At thattemperature the silica was allowed to fluidize for three hours in thedry air. Afterward, the catalyst was collected and stored under drynitrogen, where it was protected from the atmosphere until ready fortesting.

Comparative experiments were also carried out using the Cr-silicacatalyst HA30W whose support has a surface area of 500 m²/g and a porevolume of 1.6 mL/g or 969 MPI which is also a Cr-silica catalyst with asupport surface are of 300 m²/g, and a pore volume of 1.6 mL/g

Polymerization runs were made in a 2.65 liter stainless steel reactorequipped with a marine stirrer rotating at 500 rpm. The reactor wassurrounded by a stainless steel jacket through which was circulated astream of hot water which permitted precise temperature control towithin half a degree centigrade, with the help of electronic controlinstruments. Unless otherwise stated, a small amount (typically 0.05 to0.25 g) of the solid catalyst was first charged under nitrogen into thedry reactor. Next, 1.2 liter of isobutane liquid was added and thereactor heated to the standard 80° C. set temperature. Midway during theisobutane addition, triethylaluminum was added to equal 0.5 ppm of theisobutane (except in experiment 4 where 10 ppm of triethylaluminum ortriethylboron was used). Finally, ethylene was added to the reactor toequal the desired pressure, usually 2.76 MPa (400 psig), which wasmaintained during the experiment. The slurry was stirred for thespecified time, usually about one hour, and the polymerization rate wasnoted by recording the flow of ethylene into the reactor to maintain theset pressure. After the allotted time, the ethylene flow was stopped andthe reactor slowly depressurized and opened to recover a granularpolymer powder. Dry polymer powder was then removed and weighed.Activity was determined from this weight and the measured time.

Example 1

Catalyst A was a Cr/silica catalyst prepared using SYLOX-SD silicaobtained from W.R. Grace. This silica is described as a hybrid betweenprecipitated and gelled silica, and as being “reinforced.” It has asurface area of approximately 105 m²/g and a pore volume of about 1.2mL/g. This silica was then impregnated with an aqueous solution ofchromic acetate to have a 1.2 Cr/nm² chromium distribution. It was thencalcined at 550° C. and in a separate experiment at 800° C. Thesecatalysts were used to polymerize ethylene at 80° C., 400 psig, and 0.5ppm triethylaluminum as described above. The first catalyst (550° C.)produced an activity of 0.6 kg PE/g/h and the second one (800° C.)produced an activity of 1.6 kg PE/g/h. The polyethylene polymer wasanalyzed by SEC-MALS measurements which are presented in FIG. 1. FIG. 1demonstrates the broad molecular weight distribution and also the highLCB content, either as measured per million carbons, or per chain. Thepolydispersity (i.e. the weight average molecular weight (M_(w)) dividedby the number average molecular weight M_(n) or M_(w)/M_(n)) was 12.2when the catalyst was calcined to 800° C. and 26.6 when the catalyst wascalcined to 550° C.

Catalyst B was a Cr/silica-titania catalyst made by first drying theCr-impregnated SYLOX SD silica at 200° C. overnight, then impregnatingtitanium tetraisopropoxide from dry heptane solution to a level of 3 wt% Ti, then evaporating the solvent away. Finally, the dried catalyst wassized through a 35 mesh screen. The titanium-containing Cr-silicacatalyst had SYLOX-SD as the support and a chromium distribution of 1.2Cr/nm². Catalyst B was activated first at 800° C., and tested forethylene polymerization as described above, using the same conditions(80° C., 400 psig, 0.5 ppm TEA). It produced an activity of 2.8 kgPE/g/h. Another sample of Catalyst B was also activated at 550° C. andwas then tested for polymerization activity under similar conditions. Ityielded an activity of 1.6 kg PE/g/h. SEC-MALS measurements were carriedout on both polymers and are presented in FIG. 2. The molecular weightdistribution of samples produced using Catalyst B was broadened by thetitanium producing a polydispersity of 21.7 when the catalyst wascalcined to 800° C. and 27.6 when the catalyst was calcined to 550° C.These results demonstrate that the effect of including titanium in thecatalyst is to enhance LCB content and to broaden the molecular weightdistribution.

Catalyst C and Catalyst D are comparative Cr-silica catalysts. CatalystC was prepared using the precipitated silica Grace SM500 as a support,having a surface area of about 100 m²/g, which was impregnated withsufficient chromium to provide a chromium distribution of 1.2 Cr/nm² andwas calcined at 700° C. Catalyst D was the Cr-silica catalyst 969 MPI,having a surface area of about 300 m²/g, which contained 0.4 Cr/nm² andwas calcined at 850° C. Each catalyst was then used to polymerizeethylene at (80° C., 300 psig, 0.5 ppm TEA) with ethylene concentrationsranging from 0.9 mol/L. Catalyst C produced an activity of 0.1 kg PE/g/hand polymer having a polydispersity of 10.9, while Catalyst D producedan activity of 0.5 kg PE/g/h and polymer having a polydispersity of 9.4.SEC-MALS measurements are presented in FIG. 3 on both polymers. Acomparison of FIG. 3 to FIG. 1 and FIG. 2 demonstrates the broadenedmolecular weight distributions observed for catalysts having alow-surface-area, highly reinforced support.

Example 2

The effect of the surface area of the silica in the catalyst on LCB wasinvestigated further. Catalyst E was a Cr-silica catalyst prepared usingSYLOX-SD, having a pore volume of about 1.2 mL/g and a surface area ofabout 105 m²/g, as the support which was impregnated with sufficientchromium to provide a chromium distribution of 1.2 Cr/nm². Catalyst Fused W.R. Grace grade 952 silica, having a pore volume of 1.6 mL/g and asurface area of 300 m²/g, impregnated with a similar amount of chromium.Catalyst G used W.R. Grace grade HA30W, having a pore volume of 1.6 mL/gand a surface area of about 500 m²/g, also impregnated with a similaramount of chromium. Catalyst F is similar to Catalyst D. Catalysts E, F,and G were calcined at 800° C. and tested for polymerization activity.Polymers were prepared using these Cr—X catalysts of the type disclosedherein (i.e., Catalyst E) at 80° C., 400 psig and 0.5 ppm TEA. CatalystE produced polymers having a polydispersity of 12.2 and Catalyst F andCatalyst G produced polymers having polydispersities of 13.3 and 11.9respectively. The results are shown in FIG. 4.

Example 3

The effect of altering the chromium concentration on the LCB content ofthe polymers was investigated. Catalyst H was prepared by impregnatingSYLOX-SD with chromic acetate to provide a chromium distribution of 3.5Cr/nm². The impregnated support was then calcined at 800° C. asdescribed above. When tested for ethylene polymerization activityCatalyst H produced an activity of 2.3 kg PE/g/h and polymer having apolydispersity of 10.1 as shown in FIG. 5. Referring to FIG. 5, thepolymer produced from Catalyst H displayed a LCB content which peaked atover 40 branches per million carbons, and over 2.0 branches per chain.

Example 4

The effect of polymerizing in the presence of a cocatalyst on the LCBcontent of the polymers was investigated. In two separate runs, CatalystA (800° C.) was tested with either 10 ppm of triethylaluminum (based onthe weight of the isobutane diluent) or with 10 ppm of triethylboronadded to the reactor. Under both reaction conditions, the catalysts werequite active, yielding activities of 1.8 and 3.3 kg PE/g/h respectively.They produced polymer with broadened MW distribution (polydispersitiesof 16.1 and 17.5 respectively). The SEC-MALS results on these polymersare shown in FIG. 6. Referring to the top part of FIG. 6, the resultsdemonstrate that both cocatalysts extended the high-molecular weightside of the molecular weight distribution. Referring to the top part ofFIG. 6, the results indicate that cocatalysts do not seem to haveincreased the amount of LCB. However, the LCB peak has been shifted tohigher molecular weight. In the bottom part of FIG. 6, where the LCB isplotted per chain, it was observed that the LCB has been pushed tohigher molecular weight demonstrating that the LCB/chain is quite highwhen cocatalysts are used. For example, the polymer produced usingtriethylboron displays a LCB peak of approximately 2 branches per chain.Notice also that the LCB content seems to have been pushed out to highermolecular weight by the use of cocatalysts, which produces higher levelsof rheological elasticity.

Example 5

The effect of polymerizing in the presence of a low monomerconcentration on the LCB content of the polymers was investigated.Catalyst F was used to polymerize ethylene under varying ethyleneconcentrations, including as low as 0.2 mol/L ethylene. Thepolymerizations were carried out at 80° C. with 0.5 ppm TEA. The resultsof this experiment are summarized, along with all the previousexperiments, in Table 1 below. FIG. 7 depicts the effect of varying theconcentration of ethylene monomer on the LCB content. Low ethyleneconcentration was effective at raising the level of LCB, but it alsolowered the activity more.

TABLE 1 LCB Peak Experiment Activity Mw LCB/10⁶ total Example/CatalystCatalyst & Run Conditions Kg PE/h Kg/mol Mw/Mn carbon atoms Ex1/Catalyst A Cr/SiO₂, 550° C. 0.6 543 26.6 10 Ex 1/Catalyst A Cr/SiO₂,800° C. 1.6 380 12.2 24 Ex 1/Catalyst B Cr/SiO₂-TiO₂ 550° C. 1.6 30021.7 23 Ex 1/Catalyst B Cr/SiO₂-TiO₂ 800° C. 2.8 218 27.6 35 Ex1/Catalyst C Cr/SiO₂, SM500, 800° C. 0.1 286 10.9 28 Ex 1/Catalyst DCr/SiO₂, 800° C., 300 m²/g 0.5 262 9.4 10 Ex 2/Catalyst G Cr/SiO₂, 800°C., 500 m²/g 2.4 389 11.9 1.5 Ex 2/Catalyst F Cr/SiO₂, 800° C., 300 m²/g3.4 345 13.3 15 Ex 2/Catalyst E Cr/SiO₂, 800° C., 100 m²/g 1.6 423 12.227 Ex 3/Catalyst H Cr/SiO₂, 3.5 Cr/nm², 800° C. 2.3 355 10.1 43 Ex4/Catalyst A Cr/SiO₂, 800° C., BEt₃ 3.3 481 17.5 24 Ex 4/Catalyst ACr/SiO₂, 800° C., AlEt₃ 1.8 460 16.1 24 Ex 5/Catalyst F Cr/SiO₂, 800°C., 300 m²/g, 0.2 mol/L 0.9 308 9.9 19 Ex 5/Catalyst F Cr/SiO₂, 800° C.,300 m²/g, 1.6 mol/L 3.4 345 11.6 15 Ex 5/Catalyst F Cr/SiO₂, 800° C.,300 m²/g, 3.1 mol/L 3.6 378 12.1 12

While various embodiments have been shown and described, modificationsthereof can be made without departing from the spirit and teachings ofthe disclosure. The embodiments described herein are exemplary only, andare not intended to be limiting. Many variations and modifications ofthe subject matter disclosed herein are possible and are within thescope of the disclosure. Where numerical ranges or limitations areexpressly stated, such express ranges or limitations should beunderstood to include iterative ranges or limitations of like magnitudefalling within the expressly stated ranges or limitations (e.g., fromabout 1 to about 10 includes, 2, 3, 4, etc.; greater than 0.10 includes0.11, 0.12, 0.13, etc.). Use of the term “optionally” with respect toany element of a claim is intended to mean that the subject element isrequired, or alternatively, is not required. Both alternatives areintended to be within the scope of the claim. Use of broader terms suchas comprises, includes, having, etc. should be understood to providesupport for narrower terms such as consisting of, consisting essentiallyof, comprised substantially of, etc.

Accordingly, the scope of protection is not limited by the descriptionset out above but is only limited by the claims which follow, that scopeincluding all equivalents of the subject matter of the claims. Each andevery claim is incorporated into the specification as an embodiment ofthe present disclosure. Thus, the claims are a further description andare an addition to the embodiments of the present disclosure. Thediscussion of a reference in the disclosure is not an admission that itis prior art to the present disclosure, especially any reference thatmay have a publication date after the priority date of this application.The disclosures of all patents, patent applications, and publicationscited herein are hereby incorporated by reference, to the extent thatthey provide exemplary, procedural or other details supplementary tothose set forth herein.

What is claimed is:
 1. A polymer having a long chain branching contentpeaking at greater than about 20 long chain branches per million carbonatoms, and a polydispersity index (M_(w)/M_(n)) of greater than about 10wherein the long chain branching decreases to approximately zero at thehigher molecular weight portion of the molecular weight distribution. 2.The polymer of claim 1 wherein polymer comprises polyethylene.
 3. Thepolymer of claim 1 wherein the polymer displays a molecular weightdistribution of greater than about
 15. 4. The polymer of claim 1 whereinthe long-chain branching content peaks at greater than about 1.0long-chain branches per chain.
 5. The polymer of claim 1 wherein thelong-chain branching content peaks at about 25 long chain branches permillion carbon atoms
 6. The polymer of claim 1 wherein the long-chainbranching content peaks at about 30 long chain branches per millioncarbon atoms
 7. The polymer of claim 1 having a melt index of from about0 dg/min to about 100 dg/min.
 8. The polymer of claim 1 having a densityof from about 0.90 g/cc to about 0.97 g/cc.
 9. A polymer having a longchain branching content peaking at greater than about 8 long chainbranches per million carbon atoms, a polydispersity index of greaterthan about 20 wherein the long chain branching decreases toapproximately zero at the higher molecular weight portion of themolecular weight distribution.
 10. The polymer of claim 9 wherein thelong-chain branching content peaks at about 20 long chain branches permillion carbon atoms
 11. The polymer of claim 9 wherein the long-chainbranching content peaks at greater than about 1.0 long-chain branchesper chain.
 12. The polymer of claim 9 wherein polymer comprisespolyethylene.
 13. A polymer having a long chain branching contentpeaking at greater than about 1 long chain branches per chain, and apolydispersity index of greater than about 10 wherein the long chainbranching decreases to approximately zero at the higher molecular weightportion of the molecular weight distribution.
 14. The polymer of claim13 wherein the long-chain branching content peaks at greater than about1.3 long-chain branches per chain and the molecular weight distributionis greater than about
 20. 15. The polymer of claim 13 wherein thelong-chain branching content peaks at greater than about 1.5 long-chainbranches per chain and the molecular weight distribution is greater thanabout
 20. 16. The polymer of claim 13 wherein the polymer comprisespolyethylene.
 17. A method of polymerizing a monomer comprisingcontacting the monomer with a chromium-supported catalyst underconditions suitable for the formation of a polymer; and recovering thepolymer wherein the chromium supported catalyst comprises a silicasupport having a surface area of less than about 200 m²/g and whereinthe polymer has a long chain branching content peaking at greater thanabout 20 long chain branches per million carbon atoms.
 18. The method ofclaim 17 wherein conditions suitable for formation of a polymer furthercomprises a cocatalyst.
 19. The method of claim 17 wherein thechromium-supported catalyst further comprises titanium.
 20. The methodof claim 17 wherein the monomer comprises ethylene and the polymercomprises polyethylene.